Feeding experiments with [1,2-C-13(2)]acetate have been used to demonstrate that the dorid nudibranchs Archidoris odhneri and A. montereyensis are capable of de novo biosynthesis of the terpenoic acid glycerides 1 and 4. Feeding experiments using [2-C-13] mevalonolactone as a precursor have shown that Sclerodoris tanya is capable of de novo biosynthesis of the terpenoid fragment of tanyolide B (7). Copyright (C) 1996 Elsevier Science Ltd